title: Biogenic volatile organic compound and respiratory CO2 emissions after 13C-labeling: online tracing of C translocation dynamics in poplar plants.
abstract: BACKGROUND
  Globally plants are the primary sink of atmospheric CO(2), but are also the major contributor of a large spectrum of atmospheric reactive hydrocarbons such as terpenes (e.g. isoprene) and other biogenic volatile organic compounds (BVOC). The prediction of plant carbon (C) uptake and atmospheric oxidation capacity are crucial to define the trajectory and consequences of global environmental changes. To achieve this, the biosynthesis of BVOC and the dynamics of C allocation and translocation in both plants and ecosystems are important.
  
  
  METHODS
  We combined tunable diode laser absorption spectrometry (TDLAS) and proton transfer reaction mass spectrometry (PTR-MS) for studying isoprene biosynthesis and following C fluxes within grey poplar (Populus x canescens) saplings. This was achieved by feeding either (13)CO(2) to leaves or (13)C-glucose to shoots via xylem uptake. The translocation of (13)CO(2) from the source to other plant parts could be traced by (13)C-labeled isoprene and respiratory (13)CO(2) emission.
  
  
  RESULTS
  In intact plants, assimilated (13)CO(2) was rapidly translocated via the phloem to the roots within 1 hour, with an average phloem transport velocity of 20.3±2.5 cm h(-1). (13)C label was stored in the roots and partially reallocated to the plants' apical part one day after labeling, particularly in the absence of photosynthesis. The daily C loss as BVOC ranged between 1.6% in mature leaves and 7.0% in young leaves. Non-isoprene BVOC accounted under light conditions for half of the BVOC C loss in young leaves and one-third in mature leaves. The C loss as isoprene originated mainly (76-78%) from recently fixed CO(2), to a minor extent from xylem-transported sugars (7-11%) and from photosynthetic intermediates with slower turnover rates (8-11%).
  
  
  CONCLUSIONS
  We quantified the plants' C loss as respiratory CO(2) and BVOC emissions, allowing in tandem with metabolic analysis to deepen our understanding of ecosystem C flux.
authors.affiliation: Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Garmisch-Partenkirchen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ghirardo
authors.forename: Jessica
authors.initials: J
authors.lastname: Gutknecht
authors.forename: Ina
authors.initials: I
authors.lastname: Zimmer
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brüggemann
authors.forename: Jörg-Peter
authors.initials: JP
authors.lastname: Schnitzler
mesh_terms: D000465:Algorithms; D001692:Biological Transport / Q000502:physiology; D002244:Carbon / Q000493:pharmacokinetics*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D019069:Cell Respiration / Q000502:physiology; D008954:Models, Biological; D009862:Online Systems / Q000295:instrumentation; D018515:Plant Leaves / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D032107:Populus / Q000378:metabolism*; D013194:Staining and Labeling / Q000295:instrumentation / Q000379:methods*; D055549:Volatile Organic Compounds / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D055549:Volatile Organic Compounds; D002245:Carbon Dioxide; D002244:Carbon